1. Field of the Invention
This invention relates to devices for indicating at a remote station temperature conditions within a storage compartment and the operating mode of the refrigerating equipment thereof and more particularly for use on air conditioned trailer trucks wherein the remote indicators are mounted on the exterior of the trailer and may be selectively displayed as a direct image for viewing from the ground when the trailer is parked or as a mirror image for viewing by the driver in the cab through a rear view mirror.
2. Description of the Prior Art
Refrigeration equipment installed in trailer trucks operate in three modes, namely, cooling, defrosting and heating for closely controlling the temperature within the cargo compartment and usually have temperature and mode indicators positioned at a location inaccessible for viewing when the trailer is in transit or from the ground when the trailer is parked.
Although the need for a highly visible indicator of temperature conditions within the trailer and the operating mode of the refrigeration equipment has long been recognized, solutions to this problem have been limited to alarm warning devices, such as a flashing light and/or buzzer, which are activated when the temperature within the trailer as determined by a sensor falls outside the range of temperature predetermined in the control circuitry. Thus, U.S. Pat. No. 3,594,752 to Alton discloses a self-contained unit in which the flashing lamp and control circuitry is contained in a housing adapted to be mounted on the outside of the trailer, the temperature sensor being attached to the end of an elongated tubular member extending from the rear of the housing to pass through an opening drilled in the wall of the trailer. U.S. Pat. No. 4,024,495 to O'Brien provides for a temperature sensing circuit within the trailer and a detection circuit and alarm located within the cab, the two circuits being electrically connected through existing wiring between the cab and trailer. These systems are merely warning devices and fail to provide the driver or others responsible for the cargo with readings of updated specific temperature readings. Recently remote temperature readouts located in the cab and connected to the trailer in a manner similar to the O'Brien patent have been made available. However, there still exists a need for a practical readout system for both temperature and mode operation, the installation of which is limited to the trailer yet which can be easily observed from both the cab while the trailer is in transit and from the ground when the trailer is parked. These updated readings of the combination of temperature and mode operation permit corrective action to be taken before and not after critical conditions prevail.